Variable area spray bar



July17, 1956 aw. CONRAD VARIABLE AREA sPAiBAR Filed Feb. 1.2. 1954 lnwvrlflnallllla l nfln 4 iaunnlanunvinlv i r U 1 a I a v z EarlW Cb/zrad v ATTORNEYS bar with flexible walls 2,155,133 Patented July 17, 1956 I 2,155,133 VARIABLE AREA smY mm Earl w. Conrad, Ber-ea, Ohio, asdgllor to the'Unlted gatleqs of America as represented by the Secretary of e Ivy Application February 12, 1954, Serlal No. 410,053 8 Claims, cl. ass-101.3 (Granted under Title 35, U. s. Code 1952 m. m

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a fuel spray device wherein the area of the nozzle is automatically varied as a function of fuel pressure.

Within the flight envelope of the present turboiet and ram jet engines of aircraft, ram air density variations occur on the order of 13 to 1. Operation at constant fuel-air ratio, therefore, requires a 13 to l variation in fuel flow. It is further understood, that in present afterburners, the maximum fuel flow is approximately 40 times greater than the minimum required fuel flow. -Hence, with simple orifice spray bars, the maximum fuel pressure would be about 1600 times the minimum pressure. Inasmuch as a simple fixed orifice spray requires a pressure of approximately pounds per square inch for suitable fuel spray, theuse of such spray bars in afterburners would require fuel pressures varying from 15 to 24,000 pounds per square inch. Present afterburner fuel pumps operate, however, at a maximum fuel pressure of only about 300 pounds per square inch, and the fuel pressure at minimum flow is only a fraction of 1 pound per square inch. The fuel pressure at minimum flow is not adequate, therefore, for fuel spray and atomization by a fixed spray bar.

It is an object of this invention, therefore, to achieve suitable spray and atomization characteristics within present fuel pump pressure limitations for all flow rates required in jet afterburners, by producing an automatic change in effective flow area of the nozzle with changes in fuel pressure.

It is another object of this invention to provide a spray bar for afterburners which will automatically provide an extremely wide range of fuel flow nozzle areas.

Another object of this invention is to provide a spray having ports therein, and having needle valves mounted on said walls, opposite each port, whereby the effective area of the ports is varied by movement of said valves when the wall is flexed by changes in pressure.

Other and invention will become apparent eration of the following detailed pended claims taken in connection ing drawings, in which:

Fig. l is a view showing a preferred embodiment of this invention;

Fig; 2 is an expanded cross sectional view of the invention taken through the line 22 in Fig. l;

Fig. 3 is a cross sectional view of the invention taken through the line 3-3 of Fig. l, and

Fig. 4 is a view similar to Fig. 3, showing the device under increased pressure.

Reference is now made to Figs. 1 to 4 of the drawing. The variable area spray bar, or nozzle, of this invention comprises a flattened, thin wall tube 10 having a sealed more specific objects and advantages of this after a careful considdescription and the apwith the accompanyz end 11. In cross section, as seen in Figs. 3 and 4, the tube is seen to comprise two flattened portions 12 and.13, and curved portions 14 and 15. The flattened portion 12 of the tube 10 is provided with a series of aligned orifices, or ports 16, while metering pins 17, having conical surfaces 18, are mounted opposite said orifices 16 on the flattened portion 13. The spray bar. 10 is connected to a suitable fuel conduit 19, through which fuel is pumped to the spray bar, as indicated by the arrow 20, convenient source (not shown). I

Thetube 10 is constructed of a strong, thin, flexible sheet metal. A material found to be suitable for the purpose of the spray bar was found to be Inconel having a thickness an inch. Any other material may be used, however, and

for certain applications, plastic materials or rubber may be suitable.

The metering pins 17 each have a larger diameter than the orifices 16, but the conical surfaces 18, which extend therethrough, provide a positive seat on the inner edge of said orifices, and under conditions of no fuel pressure in the tube 10, the orifices 16 are sealed.

As seen in Fig. 4, when the fuel pressure within the tube 10 increases, as required under operating conditions of a jet engine, the cross sectional area of the tube 11 tends to expand into the shape of a circle, and the distance between the portions 12 and 13 of the tube 10 increases. It becomes apparent, therefore, that the metering pins 17 move away from the orifices l6, and that the effective area of the orifices, as determined by the position of the conical surface 18, relative thereto, is increased with an increase in fuel pressure. Similarly, a reduction of fiuid pressure from a given pressure level will tend to return the tube to its original shape and cross sectional area, and thus move the metering pin 17 towards the orifice 16 to reduce the effective area thereof.

Since an increase .in pressure on the inner walls of a tubular member of any cross sectional configuration will tend to increase the cross sectional area thereof, and since a circle has the greatest area for any given perimeter of a geometric body, it is obvious that many configurations will be suitable for the cross sectional shape of the tube 10. For the application of the spray bar, it is only necessary that the metering pins 17 and the orifices be orientated on a diameter which will tend to increase upon the application of an increased pressure.

It is seen that if the metering pin 17 and the orifices 16 were positioned, respectively, on the portions 14 and 15 of the tube 10, the effective area of the orifices would decrease with an increase in pressure. This result would follow since the distance between portions 14 and 15 would decrease as the tube expanded in cross section, and

the metering pins would be moved toward the orifices.

This arrangement may be utilized where it is desired to maintain a substantially constant fluid flow under condition of varying fluid pressure.

The performance of the illustrated spray bar has proved successful in that satisfactory fuel spray and atomization characteristics were achieved over a wide variation of fuel pressure, and in that the variation of fuel flow with respect to pressure increase was substantially the same as the variation of fuel flow with respect to pressure decrease. The spray bar of this invention permits suitable fuel spray and atomization over a much wider range of fuel flows than is possible with any known afterburner fuel systems.

Having thus described the invention, it is apparent that many modifications and variations will become readily apparent to those skilled in the art. It is the intent, therefore, that this invention be limited only by the scope and spirit of the appended claims.

from a,

of approximately twenty-thousandths of amines What is claimed is:

l. A variable area spray nozzle comprising a relatively thin-walled tubular member of non-circular cross section, one end of said tubular member being sealed and the other end adapted to,be connected to a source of fiuid under pressure, an orifice in a wall portion of said tubular member which is closer to the axis of said member than other portions thereof, a pin in said tubular member extending from a wall portion thereof opposite said first mentioned wall portion and seating in said orifice at low pressures, whereby upon a progressive increase in pressure within said tubular member said tubular member tends to become circular in cross section and said pin is progressively withdrawn from its seat.

2. The apparatus as defined in claim I wherein the pin has a conical end.

3. The apparatus as defined in claim I wherein the two wall portions mentioned are closer together than any other two wall portions.

4. The apparatus as defined in claim 3 wherein the pin has a conical end.

5. A substantially closed thin-walled tube, said tube being of non-circular cross section, means adapted to connect said tube to a source of fluid under pressure, an

gressively withdrawn from its seat.

6. The apparatus as defined in claim 5 wherein said tube has an ovalcross section.

7. The invention as defined in claim 6 wherein the end of the pin which seats on the orifice is conical.

8. The apparatus as defined in claim 5 wherein the end oi the pin which seats on the orifice is conical.

Meme-es. Chad in the lie of this patent UNITED STATES PATENTS 1,602,047 Schultheis Oct. 5, 1926 2,303,992 Frazer et al. Dec. 1, 1942 2,630,324 Loy Mar. 3, i953 FOREIGN PATENTS 314,518 Germany Sept. 25, 1919 157,428 Great Britain May 10, 1922 will tend to be 

5. A SUBSTANTIALLY CLOSED THIN-WALLED TUBE, SAID TUBE BEING OF NON-CIRCULAR CROSS SECTION, MEANS ADAPTED TO CONNECT SAID TUBE TO A SOURCE OF FLUID UNDER PRESSURE, AN ORIFICE IN THE WALL OF SAID TUBE AND A PIN IN SAID TUBE, FIXED TO A WALL THEREOF, AND ALIGNED WITH SAID ORIFICES AND SEATED THEREON, SAID PIN AND ORIFICE BEING LOCATED ON A MINOR AXIS OF THE CROSS SECTION OF SAID TUBE, WHEREBY UPON AN INCREASE IN FLUID PRESSURE SAID TUBE WILL TEND TO BECOME CIRCULAR IN CROSS SECTION AND SAID PIN WILL BE PROGRESSIVELY WITHDRAWN FROM ITS SEAT. 